This invention relates to potentiometer drive mechanisms, and more particularly to drive mechanisms for use with a potentiometer which must be physically isolated from the operator.
When pressure transducers and other instruments employing electrical potentiometers are operated in a volatile gaseous environment, it is very important that small explosions resulting from the electrical circuitry be contained within the potentiometer housing. If permitted to propagate outside the housing they can touch off a very severe explosion. There is thus a need to adequately seal the potentiometer housing. This need is balanced, however, by the need to have access to the potentiometers to make necessary adjustments. This problem is resolved in many cases by providing a removable housing cover which is merely taken off whenever an adjustment is made. This procedure adds to the time needed to make an adjustment, however, and also exposes the electrical circuitry within the housing to outside dirt and contaminants. Another approach uses a vernier screw and spring assembly to permit adjustments to be made from the outside, without exposing the interior of the housing. While this is a distinct advantage, only a somewhat coarse adjustment can be achieved with this method, and the vernier is subject to overstressing at the opposite limits of potentiometer rotation.